Extract mean diffusivity

#1

Hi MRtrix experts,

To visualize brain tumors in my DWI images, i got the suggestion to calculate mean diffusivity maps.
Since it uses the diffusion tensor model, I selected only my lower b-values (b=0,700,1200) and left out the b=2800 shell.
I then computed the diffusion tensor (dwi2tensor dwi_input.mif -mask mask.nii dwi_dt.nii) and tried to extract the MD, which should be the same as the ADC (tensor2metric dwi_dt.nii -mask mask.nii -adc adc.nii).
However, what I end up with is just a white image with some black voxels, intensity ranging from -151 up to 124.
Does anyone have an idea on what might have gone wrong?

Thanks in advance!

Best regards,
Hannelore

#2

Hey Hannelore,

There are probably a few extreme values in your ADC map. In mrview, choose Tool, View options and set the intensity range to sensible value for ADC.

Also, make sure you use the latest dwi2tensor version as we recently fixed a bug.